This project aims to study the cross-talk between DISCI and NRG/ErbB signaling and its impact on radial neuronal migration, towards better understanding the pathophysiology of Schizophrenia (SZ) during neurodevelopment. DISC1 and NRG1 are both major susceptibility genes for SZ, and preliminary data indicates that NRG1 signaling can affect expression of DISK1. We intend to treat primary cortical neuron cultures with recombinant NRG1, NRG2, and NRG3 to study the effects of NRG signaling on DISK1 expression at the protein and mRNA level by Western blot and RT-PCR respectively. In conjunction with this treatment, we will either infect primary neurons with lentiviral vectors to express shRNA to NRG receptors ErbB2, ErbB3, or ErbB4, or pharmacologically block the PI3K/Akt, MARK, or STAT secondary signaling cascades in order to determine which receptor and downstream signaling pathway transduces these effects. Preliminary results also indicate that DISK1 expression regulates transcription of ErbB4. We will confirm this result at the protein and mRNA level using a knockout mouse model of DISK1. We have also shown that DISK1 binds directly to ErbB4;we will determine whether this interaction is necessary for DISK1 control of ErbB4 expression, by overexpressing D1SC1 missing the binding domain to ErbB4 and measurement of ErbB4 expression in primary neurons. Based on the results obtained, we will either study DISK1 effects on nuclear localization of ErbB4 by immunohistochemistry and nuclear fractionation, or interaction of nuclear D1SC1 with transcription factors which may bind to the 5'promoter region of ErbB4. We will also confirm that DISK1 can bind to the intracellular domain of ErbB4 by exogenous co- immunoprecipitation. We will perform in situ hybridization for D1SC1 in an embryonic NRG 1-knockout mouse model and for ErbB4 in a DISC1 knockout-model to confirm the above expression results in vivo. Next, we will modulate DISK1 and NRG1 expression in vivo using in utero electroporation, to study the physiological impact of these mechanisms, observing radial neuronal migration as an indicator of the functional impact of the DISC1/NRG1 pathway. Finally, we will modulate ErbB4 expression using in utero electroporation to observe its role in radial migration, and perform rescue experiments with DISK1 to study whether the DISC1/ErbB4 cross-talk plays a role in this important neurodevelopmental process. Schizophrenia is a devastating psychiatric disorder affecting an estimated 1% of Americans. This project aims to study the convergent mechanisms by which major susceptibility genes for schizophrenia (D1SC1, Neuregulins, and ErbB receptors) affect development and lead to disease pathophysiology.